The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 199 46 971.7, filed on Sep. 30, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to a device for dewatering a material web, in particular a paper or cardboard web, by driving water out of the material web by gas pressure. the device includes having at least one pressure chamber limited by at least four rolls arranged parallel to one another and arranged to form a pressure chamber of which a pressurized gas can be introduced and through which the material web can be guided.
2. Discussion of Background Information
In such a process, instead of a mechanical compression of the material web, the pressurized gas is pressed through the material web and the water is driven out of the material web in this manner.
An aspect of the invention is to produce a device of the above-mentioned type for dewatering a material web that can be used in as many functions as possible. This device for dewatering a material web, in particular a paper or cardboard web, by driving water out of the material web using gas pressure, having at least one pressure chamber limited by at least four rolls arranged parallel to one another into which a pressurized gas can be introduced and through which the material web can be guided, with the positions of the rolls being displaceable relative to one another. Moreover, the positions of the rolls can be adjusted relative to one another.
According to the invention, the geometry and the form of the pressure chamber can be changed by the adjustability of the relative arrangement of the rolls. This creates the possibility of deliberately varying the length of the path traveled by the material web inside the pressure chamber.
According to the invention, a dwell time of the material web inside the pressure chamber can be set to any desired value by adjusting the roll position. The dewatering device according to the invention can thus be used in many different functions and for a plurality of material types. In a machine for producing a paper or cardboard web, for example, the requirements for different types of paper or cardboard can be taken into account using only one dewatering device according to the invention in that, by adjusting the relative roll positions, the necessary dwell time for the respective web to be dewatered inside the pressure chamber can be set.
It is preferred for the positions of the rolls to be adjustable while maintaining a pressure chamber that is limited by the rolls at all times. By adjusting the roll positions, the pressure chamber is maintained as such. Only the geometry and/or form of the pressure chamber is changed by adjusting the rolls.
According to another preferred embodiment of the invention, two rolls lying across from one another can each automatically track an adjusting movement of at least one of the two other rolls. Thus, it is necessary to adjust the position of only one single roll because the automatic tracking of the two rolls that are facing one another assures that the desired roll configuration is set at the end of the adjusting movement.
It is preferred for each of the two rolls lying across from one another to be prestressed in contact with both of the other rolls, with the distance between the two other rolls being adjustable.
The prestressing causes the two rolls lying across from one another to be pressed against both of the other rolls and to remain in contact with the other rolls, thereby maintaining a pressure chamber limited by all four rolls, when the distance between the other two rolls is changed for the purpose of setting the desired roll configuration. It is preferred for both prestressed rolls to have a smaller diameter than the other two rolls.
According to one variant of the invention, the prestressing of the rolls can be achieved in that the prestressed rolls are each coupled by at least one prestressing device to a stationary support. The prestressing devices can, for example, be elastically deformable and, e.g., embodied as arrangements of pressure springs, each of which are supported at one end on the stationary support and are connected with the respective roll on the other end.
According to another variant of the invention, the prestressing of the rolls is achieved in that the rolls are coupled with one another by way of at least one prestressing device. The prestressing device, which is embodied, for example, as being elastically deformable and, e.g., embodied as a tension spring, attempts to move the two rolls toward one another, whereby the two prestressed rolls are pressed against both of the other rolls.
The prestressing devices can also be embodied as hydraulic or pneumatic cylinders. The contact force of the roll can be predetermined thereby using the fluid and/or gas pressure, in which connection the fluid and/or gas can be adjusted by a control and/or regulation device, in particular dependent upon the pressure prevailing in the pressure chamber. With such an adjustable prestressing device, the mechanical pressure on the material web in the entrance nip and exit nip of the pressure chamber can be varied. In this manner, a pre- and/or post compression of the material web is achieved whose effectiveness is deliberately adjustable.
In all variants of the invention listed above, the prestressed rolls are kept permanently in contact with the two other rolls so that, in the case of an adjusting movement, at least one of the two other rolls can follow the prestressed roll making the adjusting movement and a pressure chamber with the desired geometry and/or form that is limited by all four rolls is present at the end of the adjusting movement.
The present invention further provides a process for dewatering a material web, in particular a paper or cardboard web, by driving water out of the material web by gas pressure, in which a pressurized gas is introduced into at least one pressure chamber and the material web is guided through the pressure chamber. The area of effect of the pressure chamber is changed in the travel direction of the material web, in particular its effective length, for the purpose of adjusting the dewatering capacity of the area of effect of the pressure chamber.
With such a process, the dwell time of the material web in the pressure chamber, and thus the dewatering capacity, can be adjusted in the desired manner by changing the area of effect of the pressure chamber.
Advantageous embodiments of the invention are also provided in the claims, the description, and the drawings.
According to an aspect of the invention an apparatus for dewatering a material web is provided which includes at least one pressure chamber formed by at least four substantially parallel rolls, a device arranged to introduce a pressurized gas into the at least one pressure chamber, and the at least four substantially parallel rolls being displaceable relative to one another to change an effective area of the at least one pressure chamber. The material web is guided through the at least one pressure chamber.
According to another aspect of the present invention the material web is one of a paper and cardboard web. Additionally, other aspects of the present invention include driving water out of the material web using the pressurized gas. In another aspect of the present invention positions of the at least four substantially parallel rolls are adjustable while a pressure within the at least one pressure chamber is maintained.
According to a further aspect of the present invention a first pair of rolls of the at least four substantially parallel rolls are configured across from one another and a position of the first pair of rolls is adopted to follow a movement of at least one of the remaining rolls of the at least four substantially parallel rolls.
In another aspect of the present invention, the invention includes at least one prestressing device. A first pair of rolls of the at least four substantially parallel rolls are configured across from one another, the at least one prestressing device is arranged to prestress the first pair of rolls in contact with the remaining rolls of the at least four substantially parallel rolls by at least one prestressing device, and a distance between the remaining rolls is adjustable.
According to a further aspect of the present invention, the first pair of rolls have a smaller diameter than the remaining rolls of the at least four substantially parallel rolls. In another aspect of the present invention, the first pair of rolls have a substantially smaller diameter than the remaining rolls of the at least four substantially parallel rolls.
In another aspect of the present invention, the apparatus includes a roll support. One roll of the first pair of rolls is fixed firmly on the roll support and an other of the first pair of rolls is mounted for movement relative to the fixed one roll.
According to a still further aspect of the present invention at least one stationary support, wherein each roll of the first pair of rolls are coupled to the at least one stationary support by the at least one prestressing device.
Further aspects of the invention include a pressure spring arrangement. According to other aspects of the present invention the at least one prestressing device is arranged to couple said first pair of rolls to one another. According to other aspects of the present invention the at least one prestressing device is a tension spring arrangement.
According to another aspect of the present invention the at least one prestressing device is structured and arranged in such a way that prestressing force placed on said first pair of rolls is at least essentially independent of a position of said first pair of rolls. According to a further aspect of the present invention, the invention includes a belt of water absorbent material, wherein at least inside said at least one pressure chamber, the material web is arranged between a belt of water-absorbent material and membrane. According to still a further aspect of the invention, the belt of water-absorbent material comprises felt.
Further, one of the at least four substantially parallel rolls can be positionally fixed for rotation and arranged to support the material web as it is guided through the at least one pressure chamber. The one of the at least four substantially parallel rolls can include a surface at least one of grooved and blind bored. Alternatively, or additionally, the one of the at least four substantially parallel rolls may include a suction roll.
The apparatus may also include two side sealing plates arranged at opposite ends of the at least four substantially parallel rolls. At least one of the two side sealing plates may include a gas inlet coupled to the gas introduction device. At least a part of the pressurized gas introduced into the at least one pressure chamber can be introduced through said gas inlet.
According to another aspect of the present invention, a process is provided for dewatering a material web, including pressurizing at least one pressure chamber with a gas medium, guiding the material web through the pressure chamber, driving water out of the material web using gas pressure within the at least one pressure chamber, and changing an effective area of the pressure chamber so as to adjust a dewatering capacity.
In accordance with still another feature of the invention, the process may include removing the water driven out of the material web via one of a grooved and blind bored support roll.
Moreover, the process may also include removing the water driven out of the material web via one of a suctioned support roll.
In another aspect of the invention, the changing of the effective area comprises changing an effective length of the pressure chamber in a web travel direction.
According to a still further aspect of the present invention, the dewatering process can be performed using an apparatus that includes at least one pressure chamber formed by at least four substantially parallel rolls, a device arranged to introduce a pressurized gas into the at least one pressure chamber, and the at least four substantially parallel rolls being displaceable relative to one another, in which the material web is guided through the at least one pressure chamber. The process includes pressurizing the at least one pressure chamber through the introduction of the pressurized gas, and varying mechanical pressure exerted by the at least four substantially parallel rolls on the material web upon at least one of (1) entry into the at least one pressure chamber and (2) exit from the at least one pressure chamber, by changing the force with which the at least four substantially parallel rolls forming a respective nip are pressed against one another.
In accordance with a feature of the invention, the process can also include removing water from the material web through one of a grooved and blind bored surface of one of the at least four substantially parallel rolls.
According to still another feature of the instant invention, the process may include removing water from the material web through one of the at least four substantially parallel rolls which comprises a suctioned roll.
In accordance with yet another feature of the instant invention, the process may include changing an effective area of the at least one pressure chamber.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.